WASHINGTON – The Supreme Court refused Monday to block the redrawing of Pennsylvania's congressional districts, handing Republican leaders a stinging defeat and giving Democrats a chance to make important gains at the polls in November.

The high court's action completed a one-two punch against the GOP-dominated state Legislature. Last month, the justices refused to block a state Supreme Court decision that declared districts drawn by Republicans unconstitutional because of their partisan tilt.

After that ruling, the state court redrew the lines. Republicans challenged the new maps as improperly drawn and asked that 2018 elections be held under the old lines, beginning with a primary May 15.

Earlier Monday, a federal district court composed solely of judges appointed by Republican presidents rejected that effort. The three-judge panel concluded unanimously that the GOP leaders lacked standing to bring the case on behalf of the entire Legislature.

The dispute has national implications because Democrats could win back the U.S. House of Representatives in November. The court-drawn map would give them a better chance of winning several congressional races in Pennsylvania.

The two courts acted one day before the filing deadline for May's primary elections.

The Pennsylvania battle is one of many concerning so-called partisan gerrymandering by state legislatures that have raised the political stakes before the 2018 midterm elections, when control of Congress and many state legislatures is up for grabs.

The Pennsylvania Supreme Court ruled in January that the GOP-drawn map of congressional districts "plainly and palpably violates the Constitution of the Commonwealth of Pennsylvania." The judges demanded new maps within weeks and threatened to design their own if state officials did not comply.

Once the deadline had passed, the court came up with its own map — one that probably would end Republicans' ability to win 13 of the state's 18 seats in the U.S. House of Representatives. Across the country, every new opportunity for Democrats increases the party's chances of retaking the House in November. That would be a major setback for the Trump administration.

"Initial news accounts have concluded that it appears the court’s adopted map was intentionally drawn to favor the voters of the Democratic Party," state Republican leaders argued in court papers asking the justices to intervene. "The New York Times, among others, declared that 'Democrats couldn’t have asked for much more from the new map.' "

Lawyers for the League of Women Voters of Pennsylvania, which challenged the original Republican-drawn maps, along with others, said the second lawsuit merely represented "déjà vu all over again" with legal arguments that "have not improved with age."

"Their latest stay application is just another ploy to preserve congressional districts that violate Pennsylvania’s Constitution for one more election cycle," the challengers said.

The Pennsylvania court's action in January followed a federal judge's ruling weeks earlier that struck down North Carolina's similarly partisan maps. The U.S. Supreme Court temporarily blocked that ruling while it considers complaints from Wisconsin and Maryland that could result in a landmark ruling on partisan gerrymandering this spring.

The justices have been considering the Wisconsin challenge to state Assembly districts since hearing oral arguments in early October. They are scheduled to hear a challenge to one Maryland congressional district next week. The court's decisions could affect other states.

Although Pennsylvania is closely divided between Democrats and Republicans, maps drawn by the GOP in 2011 resulted in a 13-5 Republican edge in the state's congressional delegation. Similarly partisan maps produced a 10-3 GOP advantage in North Carolina, 12-4 in Ohio and 9-5 in Michigan — three states that are more closely divided between Democrats and Republicans than those numbers suggest.

The Pennsylvania map was possible because Republicans win the GOP districts with an average of 59%, while Democrats win theirs with an average of 77%. In that way, the challengers' lawsuit claimed, the Legislature "packed" Democratic voters into some districts and "cracked" them among the others.